Joan,
Something is indeed very fishy in London. The first question I would ask is
what is creating so much redo generation? 9x250MB = 2.1GB of data changes
inside of that hour. One thought may be that the database is still in hot
backup mode from a previously disturbed backup. The other is that several users
are doing a lot of temporary table creation, but not in the temp space.
What is the size of this database? Where does incoming data come from?
Are their a lot of very frequently refreshed snapshots? Do they do a full
refresh vs a fast refresh? What is the db_block_buffer hit ratio like? Having
a low hit ratio can indicate an excessively busy dbwr writing dirty blocks to
disk which can cause lots of check points.
Dick Goulet
____________________Reply Separator____________________
Author: "Joan Hsieh" <[EMAIL PROTECTED]>
Date: 2/1/2001 6:05 AM
Dear Listers,
Our database in London has tremendous cf enque lock. Since I am new here. I
checked the parameter found the log_checkpoint_interval set to 3200 and
log_checkpoint_timeout set to default (1800 sec). So I suggest to set
log_checkpoint_interval to 100000000 and log_checkpoint_timeout to 0. The
second thing I found we have average log switch is 6 t0 8 per hour. We have
40 redo logs, each of them is 250m. Our log buffer set to 1m. I believe
after we changed the parameter, the control file schema global enqueue lock
should be released. But it get worse, we have 98% control file enqueue lock
now. I think we have too many log switch (9 per hour now)and suggested to
increase the log to 500m, but our principle dba is not convinced, he think
log buffer size should play a more important role.
Any ideas,
Joan
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